This past weekend I attempted my first BIAB batch in about three years.

5 gallon batch size, with 10 pounds of grain, and a target mash temp of 154F with a 90 minute boil.

Beersmith reported the target volume as 9.1 gallons...I assumed initially that this was somehow meaning the combined volume of the water and grain, but when reading the mash specifics, it says to add 36.45 quarts of strike water at 163F. It then goes on to say the estimated post-boil volume is 6.25 gallons. Maybe that is also including the volume of the grain (which doesn't make sense)?

Just looking at the numbers, I knew something was wrong with the calculations, so I added 8 gallons of water instead of the recommended 9, and still ended up having to boil an extra 30 minutes or so to get to my target volume/gravity. Intuitively I also thought the strike water temperature sounded high, but I figured with the lower volume, maybe it would be OK...I was wrong. I ended up at a mash temp of over 160F after doughing in, and had to make quick adjustements while recirculating in order to get the mash temp down to the expected range.

Also, in general I feel like the "brewsheet" and "recipe" instruction boilerplate for mashing/boiling works OK for a typical 2 or 3 vessel system, but for BIAB the numbers, descriptions of the process, etc. don't work and I found them to be confusing. Thankfully, I have done it before, so it wasn't an issue as I just ignored them for the most part, but for new AG brewers, this would be a serious problem.